Gully plugging using check dams

Small dam structures constructed across erosion gullies

Check dams are small low structures built across a gully or a channel to prevent them from deepening further. These small dams reduce the speed of water flow and minimise the erosive power of runoff. They also promote the deposition of eroded materials to further stabilise the gullies.

Two gullies adjacent to a degraded area of communal grazing land were controlled by constructing check dams and with vegetative measures including planting bamboo. The main purpose was to control the further development of the gullies, which were affecting the adjacent grazing land and blocking a downstream irrigation channel. The site is community land used by the 40 households (240 people) of Dhotra village in the intensively used Jhikhu Khola watershed. Irrigated cropland lies downstream from the site, whilst the site itself is bordered by grazing land, degraded sal-dominated forest, and rainfed forward-sloping terraces.

The check dams were made of old cement bags filled with soil and were 1m high with 0.5m deep foundations. The check dams were spaced so that a line joining the top of two adjacent dams had about a 3% slope gradient. Twenty-four check dams were built in the two gullies using a total of 2400 filled cement bags. Forty clumps

of bamboo were planted between the dams for stabilisation.

All that is needed to maintain this technology is to inspect the condition of the check dams occasionally, especially before and after the monsoon. Displaced bags should be replaced and the water courses cleared of branches and big stones. Further planting should be carried out if needed.

The case study area has a distinct dry season from November to May and a wet monsoon period from June to October. Annual rainfall is around 1200 mm. The site has red soils that are highly weathered and, if not properly managed, are very susceptible to erosion.

Achievement

Due to the high establishment costs, the short term benefit for the community only matches the costs. However, in the long-term the environmental benefit of rehabilitated land is high, and economic benefit is positive.